Polymer, resist composition and patterning process

ABSTRACT

A polymer comprising recurring units of formula (1) and/or (2) wherein R 1  and R 2  are H, C 1-15  alkyl, acyl or alkylsulfonyl or C 2-15  alkoxycarbonyl or alkoxyalkyl which may have halogen substituents; R 3  and R 4  are H, C 1-15  alkyl or alkoxy or C 2-15 , alkoxyalkyl which may have halogen substituents, and R 3  and R 4  may together bond with the carbon atom to form an aliphatic ring, or R 3  and R 4 , taken together, may be an oxygen atom; and k=0 or 1, and having a Mw of 1,000-500,000 is novel. A resist composition comprising the polymer as a base resin is sensitive to high-energy radiation, has excellent sensitivity, resolution, etching resistance, and minimized swell and lends itself to micropatterning with electron beams or deep-UV.

This invention relates to (i) a polymer comprising specific recurringunits, (ii) a resist composition comprising the polymer as a base resin,and (iii) a patterning process using the resist composition.

BACKGROUND OF THE INVENTION

While a number of recent efforts are being made to achieve a finerpattern rule in the drive for higher integration and operating speeds inLSI devices, deep-ultraviolet lithography is thought to hold particularpromise as the next generation in microfabrication technology. Inparticular, photolithography using a KrF or ArF excimer laser as thelight source is strongly desired to reach the practical level as themicropatterning technique capable of achieving a feature size of 0.3 μmor less.

For resist materials for use with a KrF excimer lasers,polyhydroxystyrene having a practical level of transmittance and etchingresistance is, in fact, a standard base resin. For resist materials foruse with ArF excimer lasers, polyacrylic or polymethacrylic acidderivatives and polymers containing aliphatic cyclic compounds in thebackbone are under investigation. All these polymers have advantages anddisadvantages, and none of them have been established as the standardbase resin.

More particularly, resist compositions using derivatives of polyacrylicor polymethacrylic acid have the advantages of high reactivity ofacid-decomposable groups and good substrate adhesion and give relativelysatisfactory results with respect to sensitivity and resolution, buthave extremely low etching resistance and are impractical because theresin backbone is weak. On the other hand, resist compositions usingpolymers containing alicyclic compounds in their backbone have apractically acceptable level of etching resistance because the resinbackbone is robust, but are very low in sensitivity and resolutionbecause the reactivity of acid-decomposable protective groups isextremely low as compared with those on the (meth)acrylic polymers.Since the backbone of the resin is too robust, substrate adhesion ispoor. These compositions are thus impractical as well.

Both the (meth)acrylic and alicyclic backbone systems commonly have theproblem of pattern disruption due to swelling of resist film. Resistcompositions based on these systems have been designed so as to improvetheir resolution performance by increasing the difference in dissolutionrate before and after exposure, and as a consequence, they eventuallybecome highly hydrophobic. Highly hydrophobic resist compositions, whenapplied as a film and processed with a developer, can maintain the filmtenaciously in unexposed regions and allow the film to beinstantaneously dissolved in over-exposed regions, while relativelybroad exposed regions therebetween allow penetration of the developer,but are kept undissolved, that is, swollen. At the very small patternsize for which ArF excimer laser is actually used, those resistcompositions which allow adjacent pattern strips to be joined togetherand disrupted on account of swelling are rejected. While a finer patternrule is being demanded, there is a need to have a resist material whichis not only satisfactory in sensitivity, resolution, and etchingresistance, but fully restrained from swelling.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide (i) apolymer having improved reactivity, robustness and substrate adhesion aswell as minimized swell during development, (ii) a resist compositioncomprising the polymer as a base resin, which has a higher resolutionand etching resistance than conventional resist compositions, and (iii)a patterning process using the resist composition.

It has been found that novel polymers comprising recurring units of thefollowing general formula (1) and/or (2) and having a weight averagemolecular weight of 1,000 to 500,000, which are produced by the methodto be described later, have improved reactivity, robustness or rigidityand substrate adhesion as well as an appropriately high solubility andminimized swell in a developer; that a resist composition comprising thepolymer as the base resin has a high resolution and etching resistance;and that this resist composition lends itself to precisemicropatterning.

In a first aspect, the invention provides a polymer comprising recurringunits of the following general formula (1) and/or (2) and having aweight average molecular weight of 1,000 to 500,000:

Herein, R¹ and R⁷ each are hydrogen, a straight, branched or cyclicalkyl, acyl or alkylsulfonyl group of 1 to 15 carbon atoms or astraight, branched or cyclic alkoxycarbonyl or alkoxyalkyl group of 2 to15 carbon atoms, in which some or all of the hydrogen atoms onconstituent carbon atoms may be substituted with halogen atoms. R³ andR⁴ each are hydrogen, a straight, branched or cyclic alkyl or alkoxygroup of 1 to 15 carbon atoms, or a straight, branched or cyclicalkoxyalkyl group of 2 to 15 carbon atoms, in which some or all of thehydrogen atoms on constituent carbon atoms may be substituted withhalogen atoms, and R³ and R⁴ may together bond with the carbon atom toform an aliphatic ring having 4 to 8 carbon atoms, or R³ and R⁴, takentogether, may be an oxygen atom. The letter k is 0 or 1.

In one preferred embodiment, the polymer comprises, in addition to therecurring units of formula (1) and/or (2), recurring units of thefollowing general formula (3).

Herein R⁵ is hydrogen, methyl or CH₂CO₂R⁷; R⁶ is hydrogen, methyl orCO₂R⁷; R⁷ is a straight, branched or cyclic alkyl group of 1 to 15carbon atoms; R⁸ is an acid labile group; R⁹ is a halogen atom, ahydroxyl group, a straight, branched or cyclic alkoxy, acyloxy oralkylsulfonyloxy group of 1 to 15 carbon atoms, or a straight, branchedor cyclic alkoxycarbonyloxy or alkoxyalkoxy group of 2 to 15 carbonatoms, in which some or all of the hydrogen atoms on constituent carbonatoms may be substituted with halogen atoms; Z is a single bond or astraight, branched or cyclic (p+2)-valent hydrocarbon group of 1 to 5carbon atoms in which at least one methylene may be substituted withoxygen to form a chain-like or cyclic ether or two hydrogen atoms on acommon carbon may be substituted with oxygen to form a ketone; k is 0 or1, and p is 0, 1 or 2.

In another preferred embodiment, the polymer comprises, in addition tothe recurring units of formula (1) and/or (2), recurring units of thefollowing general formulae (3) and (4):

Herein k, p and R⁵ to R⁹ are as defined above, Y is —O— or —(NR¹⁰)—, andR¹⁰ is hydrogen or a straight, branched or cyclic alkyl group of 1 to 15carbon atoms.

In a further preferred embodiment, the polymer comprises, in addition tothe recurring units of formula (1) and/or (2), recurring units of thefollowing general formula (5) alone or in combination with recurringunits of the following general formula (3), and recurring units of thefollowing general formula (4):

Herein k, p, R⁵ to R⁹ and Y are as defined above.

In a second aspect, the invention provides a resist compositioncomprising the polymer defined above.

In a third aspect, the invention provides a process for forming a resistpattern comprising the steps of applying the resist composition definedabove onto a substrate to form a coating; heat treating the coating andthen exposing it to high-energy radiation or electron beams through aphoto mask; and optionally heat treating the exposed coating anddeveloping it with a developer.

The polymers comprising recurring units of formula (1) and/or (2) havehigh rigidity since bridged aliphatic rings are incorporated in thebackbone. Unlike polar groups introduced at a position spaced from thebackbone, highly polar ether sites incorporated within the backboneensure that transition from penetration of a developer to dissolution ofthe resin rapidly takes place within a time too short for swelling tooccur. Additionally, even a minor proportion of recurring units offormula (1) and/or (2) introduced is fully effective for achieving theswell-suppressing and substrate-adhering effects. This, in turn, allowsunits capable of establishing a differential dissolution rate, andtypically blocked carboxylic units, to be incorporated in a relativelyhigh proportion, which eventually leads to enhancement of sensitivityand resolution. Therefore, a resist composition using the polymer as abase resin satisfies all the performance factors of sensitivity,resolution and etch resistance, is fully restrained from swelling upondevelopment, and is thus very useful in forming micropatterns.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Polymer

Polymers or high molecular weight compounds comprising recurring unitsof the following general formula (1) and/or (2) according to theinvention are novel. The polymers have a weight average molecular weightof 1,000 to 500,000:

Herein, R¹ and R² each are hydrogen, a straight, branched or cyclicalkyl, acyl or alkylsulfonyl group of 1 to 15 carbon atoms or astraight, branched or cyclic alkoxycarbonyl or alkoxyalkyl group of 2 to15 carbon atoms, in which some or all of the hydrogen atoms onconstituent carbon atoms may be substituted with halogen atoms.Illustrative examples include hydrogen, methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,cyclopentyl, cyclohexyl, ethylcyclopentyl, butylcyclopentyl,ethylcyclohexyl, butylcyclohexyl, adamantyl, ethyladamantyl,butyladamantyl, formyl, acetyl, ethylcarbonyl, pivaloyl,methanesulfonyl, ethanesulfonyl, n-butanesulfonyl, trifluoroacetyl,trichloroacetyl, 2,2,2-trifluoroethylcarbonyl, methoxymethyl,1-ethoxyethyl, 1-ethoxypropyl, 1-tert-butoxyethyl, 1-cyclohexyloxyethyl,2-tetrahydrofuranyl, 2-tetrahydropyranyl, methoxycarbonyl,ethoxycarbonyl, and tert-butoxycarbonyl.

R³ and R⁴ each are hydrogen, a straight, branched or cyclic alkyl oralkoxy group of 1 to 15 carbon atoms, or a straight, branched or cyclicalkoxyalkyl group of 2 to 15 carbon atoms, in which some or all of thehydrogen atoms on constituent carbon atoms may be substituted withhalogen atoms. Examples include hydrogen, methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,cyclopentyl, cyclohexyl, ethylcyclopentyl, butylcyclopentyl,ethylcyclohexyl, butylcyclohexyl, adamantyl, ethyladamantyl,butyladamantyl, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy,sec-butoxy, tert-butoxy, tert-amyloxy, n-pentoxy, n-hexyloxy,cyclopentyloxy, cyclohexyloxy, ethylcyclopentyloxy, butylcyclopentyloxy,ethylcyclohexyloxy, butylcyclohexyloxy, adamantyloxy, ethyladamantyloxy,butyladamantyloxy, methoxymethyl, 1-ethoxyethyl, 1-ethoxypropyl,1-tert-butoxyethyl, 1-cyclohexyloxyethyl, 2-tetrahydrofuranyl and2-tetrahydropyranyl. Alternatively, R³ and R⁴ may together bond with thecarbon atom to form an aliphatic ring having 4 to 8 carbon atoms, or R³and R⁴, taken together, may be an oxygen atom. The letter k is equal to0 or 1.

More specifically, the polymers of the invention are divided into thefollowing three subgenuses of polymers.

Subgenus (I) include polymers comprising, in addition to the recurringunits of formula (1) and/or (2), recurring units of the followinggeneral formula (3):

Herein R⁵ is hydrogen, methyl or CH₂CO₂R⁷; R⁶ is hydrogen, methyl orCO₂R⁷; R⁷ is a straight, branched or cyclic alkyl group of 1 to 15carbon atoms; R⁸ is an acid labile group; R⁹ is a halogen atom, ahydroxyl group, a straight, branched or cyclic alkoxy, acyloxy oralkylsulfonyloxy group of 1 to 15 carbon atoms, or a straight, branchedor cyclic alkoxycarbonyloxy or alkoxyalkoxy group of 2 to 15 carbonatoms, in which some or all of the hydrogen atoms on constituent carbonatoms may be substituted with halogen atoms; Z is a single bond or astraight, branched or cyclic (p+2)-valent hydrocarbon group of 1 to 5carbon atoms, in which at least one methylene may be substituted with anoxygen atom to form a chain-like or cyclic ether or two hydrogen atomson a common carbon may be substituted with an oxygen atom to form aketone; k is 0 or 1, and p is 0, 1 or 2.

Subgenus (II) include polymers comprising, in addition to the recurringunits of formula (1) and/or (2), recurring units of the followinggeneral formulae (3) and (4):

Herein k, p and R⁵ to R⁹ are as defined above, Y is —O— or —(NR¹⁰)—, andR¹⁰ is hydrogen or a straight, branched or cyclic alkyl group of 1 to 15carbon atoms.

Subgenus (III) include polymers comprising, in addition to the recurringunits of formula (1) and/or (2), recurring units of the followinggeneral formula (5) alone or in combination with recurring units of thefollowing general formula (3), and recurring units of the followinggeneral formula (4):

Herein k, p, R⁵ to R⁹ and Y are as defined above.

More particularly, R⁵ is hydrogen, methyl or CH₂CO₂R⁷. R⁶ is hydrogen,methyl or CO₂R⁷. R⁷ stands for straight, branched or cyclic alkyl groupsof 1 to 15 carbon atoms, such as, for example, methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,cyclopentyl, cyclohexyl, ethylcyclopentyl, butylcyclopentyl,ethylcyclohexyl, butylcyclohexyl, adamantyl, ethyladamantyl andbutyladamantyl. R⁸ stands for acid labile groups to be described later.

R⁹ is a halogen atom, a hydroxyl group, a straight, branched or cyclicalkoxy, acyloxy or alkylsulfonyloxy group of 1 to 15 carbon atoms, or astraight, branched or cyclic alkoxycarbonyloxy or alkoxyalkoxy group of2 to 15 carbon atoms, in which some or all of the hydrogen atoms onconstituent carbon atoms may be substituted with halogen atoms.Exemplary of R⁹ are fluoro, chloro, bromo, hydroxy, methoxy, ethoxy,propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, tert-amyloxy,n-pentoxy, n-hexyloxy, cyclopentyloxy, cyclohexyloxy,ethylcyclopentyloxy, butylcyclopentyloxy, ethylcyclohexyloxy,butylcyclohexyloxy, adamantyloxy, ethyladamantyloxy, butyladamantyloxy,formyloxy, acetoxy, ethylcarbonyloxy, pivaloyloxy, methanesulfonyloxy,ethanesulfonyloxy, n-butanesulfonyloxy, trifluoroacetoxy,trichloroacetoxy, 2,2,2-trifluoroethylcarbonyloxy, methoxymethoxy,1-ethoxyethoxy, 1-ethoxypropoxy, 1-tert-butoxyethoxy,1-cyclohexyloxyethoxy, 2-tetrahydrofuranyloxy, 2-tetrahydropyranyloxy,methoxycarbonyloxy, ethoxycarbonyloxy, and tert-butoxycarbonyloxy.

Y is —O— or —(NR¹⁰)—, and R¹⁰ is hydrogen or a straight, branched orcyclic alkyl group of 1 to 15 carbon atoms, examples of which are asillustrated for R⁷.

Z is a single bond or a straight, branched or cyclic (p+2)-valenthydrocarbon group of 1 to 5 carbon atoms, in which at least onemethylene may be substituted with an oxygen atom to form a chain-like orcyclic ether or two hydrogen atoms on a common carbon may be substitutedwith an oxygen atom to form a ketone. As noted above, p is 0, 1 or 2. Incase of p=0, for example, exemplary Z groups are methylene, ethylene,trimethylene, tetramethylene, pentamethylene, hexamethylene,1,2-propanediyl, 1,3-butanediyl, 1-oxo-2-oxapropane-1,3-diyl,3-methyl-1-oxo-2-oxabutane-1,4-diyl. In case of p≠0, exemplary Z groupsare (p+2)-valent groups obtained by eliminating one or two hydrogenatoms from the above-exemplified groups.

The acid labile groups represented by R⁸ may be selected from a varietyof such groups. Examples of the acid labile group are groups of thefollowing general formulae (Li) to (L4), tertiary alkyl groups of 4 to20 carbon atoms, preferably 4 to 15 carbon atoms, trialkylsilyl groupsin which each alkyl moiety has 1 to 6 carbon atoms, and oxoalkyl groupsof 4 to 20 carbon atoms:

In these formulae and throughout the specification, the broken linedenotes a free valence bond. R^(L01) and R^(L02) are hydrogen orstraight, branched or cyclic alkyl groups of 1 to 18 carbon atoms,preferably 1 to 10 carbon atoms. Exemplary alkyl groups include methyl,ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl,cyclohexyl, 2-ethylhexyl, and n-octyl. R^(L03) is a monovalenthydrocarbon group of 1 to 18 carbon atoms, preferably 1 to 10 carbonatoms, which may contain a hetero atom such as oxygen, examples of whichinclude unsubstituted straight, branched or cyclic alkyl groups andstraight, branched or cyclic alkyl groups in which some hydrogen atomsare replaced by hydroxyl, alkoxy, oxo, amino, alkylamino or the like.Illustrative examples are the substituted alkyl groups shown below:

A pair of R^(L01) and R^(L02), R^(L01) and R^(L03) or R^(L02) andR^(L03) may form a ring. Each of R^(L01), R^(L02) and R^(L03) is astraight or branched alkylene group of 1 to 18 carbon atoms, preferably1 to 10 carbon atoms when they form a ring.

R^(L04) is a tertiary alkyl group of 4 to 20 carbon atoms, preferably 4to 15 carbon atoms, a trialkylsilyl group in which each alkyl moiety has1 to 6 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms, or agroup of formula (L1). Exemplary tertiary alkyl groups are tert-butyl,tert-amyl, 1,1-diethylpropyl, 2-cyclopentylpropan-2-yl,2-cyclohexylpropan-2-yl, 2-(bicyclo[2.2.1]heptan-2-yl)propan-2-yl,2-(adamantan-1-yl)propan-2-yl, 1-ethylcyclopentyl, 1-butylcyclopentyl,1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl,1-ethyl-2-cyclohexenyl, 2-methyl-2-adamantyl, and 2-ethyl-2-adamantyl.Exemplary trialkylsilyl groups are trimethylsilyl, triethylsilyl, anddimethyl-tert-butylsilyl. Exemplary oxoalkyl groups are 3-oxocyclohexyl,4-methyl-2-oxooxan-4-yl, and 5-methyl-2-oxooxolan-5-yl. Letter y is aninteger of 0 to 6.

R^(L05) is a monovalent hydrocarbon group of 1 to 8 carbon atoms whichmay contain a hetero atom or a substituted or unsubstituted aryl groupof 6 to 20 carbon atoms. Examples of the monovalent hydrocarbon groupwhich may contain a hetero atom include straight, branched or cyclicalkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, andcyclohexyl, and substituted groups in which some hydrogen atoms on theforegoing groups are substituted with hydroxyl, alkoxy, carboxy,alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio,sulfo or other groups. Exemplary aryl groups are phenyl, methylphenyl,naphthyl, anthryl, phenanthryl, and pyrenyl. Letter m is equal to 0 or1, n is equal to 0, 1, 2 or 3, and 2m+n is equal to 2 or 3.

R^(L06) is a monovalent hydrocarbon group of 1 to 8 carbon atoms whichmay contain a hetero atom or a substituted or unsubstituted aryl groupof 6 to 20 carbon atoms. Examples of these groups are the same asexemplified for R^(L05).

R^(L07) to R^(L16) independently represent hydrogen or monovalenthydrocarbon groups of 1 to 15 carbon atoms which may contain a heteroatom. Exemplary hydrocarbon groups are straight, branched or cyclicalkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, n-octyl, n-nonyl,n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl,cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl and cyclohexylbutyl,and substituted ones of these groups in which some hydrogen atoms arereplaced by hydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino,alkylamino, cyano, mercapto, alkylthio, sulfo or other groups.Alternatively, R^(L07) to R^(L16) ₁, taken together, form a ring (forexample, a pair of R^(L07) and R^(L08), R^(L07) and R^(L09), R^(L08) andR^(L10), R^(L09) and R^(L10), R^(L11) and R^(L12), R^(L13) and R^(L14),or a similar pair form a ring). Each of R^(L07) to R^(L16) represents adivalent C₁-C₁₅ hydrocarbon group which may contain a hetero atom, whenthey form a ring, examples of which are the ones exemplified above forthe monovalent hydrocarbon groups, with one hydrogen atom beingeliminated. Two of R^(L07) to R^(L16) which are attached to adjoiningcarbon atoms (for example, a pair of R^(L07) and R^(L09), R^(L09) andR^(L15), R^(L13) and R^(L15), or a similar pair) may bond togetherdirectly to form a double bond.

Of the acid labile groups of formula (L1), the straight and branchedones are exemplified by the following groups:

Of the acid labile groups of formula (L1), the cyclic ones are, forexample, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Examples of the acid labile groups of formula (L2) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

Examples of the acid labile groups of formula (L3) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl,1-methylcyclohexyl, 1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl,3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl, and3-ethyl-1-cyclohexen-3-yl groups.

The acid labile groups of formula (L4) are exemplified by the followinggroups:

Examples of the tertiary alkyl groups of 4 to 20 carbon atoms,trialkylsilyl groups in which each alkyl moiety has 1 to 6 carbon atoms,and oxoalkyl groups of 4 to 20 carbon atoms are as exemplified forR^(L04).

Illustrative, non-limiting, examples of the recurring units of formula(1) are given below:

Illustrative, non-limiting, examples of the recurring units of formula(2) are given below:

Illustrative, non-limiting, examples of the recurring units of formula(3) are given below:

Illustrative, non-limiting, examples of the recurring units of formula(5) are given below:

If desired, the polymers of the invention may further contain recurringunits of one or more types selected from units of the following generalformulae (M1) to (M8):

Herein, R⁰⁰¹ is hydrogen, methyl or CH₂CO₂R⁰⁰³. R⁰⁰² is hydrogen, methylor CO₂R⁰⁰³. R⁰⁰³ is a straight, branched or cyclic alkyl group of 1 to15 carbon atoms. R⁰⁰⁴ is hydrogen or a monovalent hydrocarbon group of 1to 15 carbon atoms having a carboxyl or hydroxyl group. At least one ofR⁰⁰⁵ to R⁰⁰⁸ represents a monovalent hydrocarbon group of 1 to 15 carbonatoms having a carboxyl or hydroxyl group while the remaining R'sindependently represent hydrogen or a straight, branched or cyclic alkylgroup of 1 to 15 carbon atoms. Alternatively, R⁰⁰⁵ to R⁰⁰⁸, takentogether, may form a ring, and in that event, at least one of R⁰⁰⁵ toR⁰⁰⁸ is a divalent hydrocarbon group of 1 to 15 carbon atoms having acarboxyl or hydroxyl group, while the remaining R's are independentlysingle bonds or straight, branched or cyclic alkylene groups of 1 to 15carbon atoms. R⁰⁰⁹ is a monovalent hydrocarbon group of 2 to 15 carbonatoms containing at least one partial structure selected from amongether, aldehyde, ketone, ester, carbonate, acid anhydride, amide andimide. At least one of R⁰¹⁰ to R⁰¹³ is a monovalent hydrocarbon group of2 to 15 carbon atoms containing at least one partial structure selectedfrom among ether, aldehyde, ketone, ester, carbonate, acid anhydride,amide and imide, while the remaining R's are independently hydrogen orstraight, branched or cyclic alkyl groups of 1 to 15 carbon atoms. R⁰¹⁰to R⁰¹³, taken together, may form a ring, and in that event, at leastone of R⁰¹⁰ to R⁰¹³ is a divalent hydrocarbon group of 1 to 15 carbonatoms containing at least one partial structure selected from amongether, aldehyde, ketone, ester, carbonate, acid anhydride, amide andimide, while the remaining R's are independently single bonds orstraight, branched or cyclic alkylene groups of 1 to 15 carbon atoms.R⁰¹⁴ is a polycyclic hydrocarbon group having 7 to 15 carbon atoms or analkyl group containing a polycyclic hydrocarbon group. R⁰¹⁵ is an acidlabile group. X is CH₂ or an oxygen atom. Letter k is equal to 0 or 1.

More illustratively, R⁰⁰³ is a straight, branched or cyclic alkyl groupof 1 to 15 carbon atoms, for example, methyl, ethyl, propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,cyclopentyl, cyclohexyl, ethylcyclopentyl, butylcyclopentyl,ethylcyclohexyl, butylcyclohexyl, adamantyl, ethyladamantyl, andbutyladamantyl.

R⁰⁰⁴ is hydrogen or a monovalent hydrocarbon group of 1 to 15 carbonatoms having a carboxyl or hydroxyl group, for example, hydrogen,carboxyethyl, carboxybutyl, carboxycyclopentyl, carboxycyclohexyl,carboxynorbornyl, carboxyadamantyl, hydroxyethyl, hydroxybutyl,hydroxycyclopentyl, hydroxycyclohexyl, hydroxynorbornyl, andhydroxyadamantyl.

At least one of R⁰⁰⁵ to R⁰⁰⁸ represents a monovalent hydrocarbon groupof 1 to 15 carbon atoms having a carboxyl or hydroxyl group while theremaining R's independently represent hydrogen or a straight, branchedor cyclic alkyl group of 1 to 15 carbon atoms. Examples of the carboxylor hydroxyl-bearing monovalent hydrocarbon group of 1 to 15 carbon atomsinclude carboxy, carboxymethyl, carboxyethyl, carboxybutyl,hydroxymethyl, hydroxyethyl, hydroxybutyl, 2-carboxyethoxycarbonyl,4-carboxybutoxycarbonyl, 2-hydroxyethoxycarbonyl,4-hydroxybutoxycarbonyl, carboxycyclopentyloxycarbonyl,carboxycyclohexyloxycarbonyl, carboxynorbornyloxycarbonyl,carboxyadamantyloxycarbonyl, hydroxycyclopentyloxycarbonyl,hydroxycyclohexyloxycarbonyl, hydroxynorbornyloxycarbonyl, andhydroxyadamantyloxycarbonyl. Examples of the straight, branched orcyclic alkyl group of 1 to 15 carbon atoms are the same as exemplifiedfor R⁰⁰³.

Alternatively, R⁰⁰⁵ to R⁰⁰⁸, taken together, may form a ring, and inthat event, at least one of R⁰⁰⁵ to R⁰⁰⁸ is a divalent hydrocarbon groupof 1 to 15 carbon atoms having a carboxyl or hydroxyl group, while theremaining R's are independently single bonds or straight, branched orcyclic alkylene groups of 1 to 15 carbon atoms. Examples of the carboxylor hydroxyl-bearing divalent hydrocarbon group of 1 to 15 carbon atomsinclude the groups exemplified as the carboxyl or hydroxyl-bearingmonovalent hydrocarbon group, with one hydrogen atom eliminatedtherefrom. Examples of the straight, branched or cyclic alkylene groupsof 1 to 15 carbon atoms include the groups exemplified for R⁰⁰³ ₁ withone hydrogen atom eliminated therefrom.

R⁰⁰⁹ is a monovalent hydrocarbon group of 2 to 15 carbon atomscontaining at least one partial structure selected from among ether,aldehyde, ketone, ester, carbonate, acid anhydride, amide and imide, forexample, methoxymethyl, methoxyethoxymethyl, 2-oxooxolan-3-yl,2-oxooxolan-4-yl, 4,4-dimethyl-2-oxooxolan-3-yl,4-methyl-2-oxooxan-4-yl, 2-oxo-1,3-dioxolan-4-ylmethyl, and5-methyl-2-oxooxolan-5-yl.

At least one of R⁰¹⁰ to R⁰¹³ is a monovalent hydrocarbon group of 2 to15 carbon atoms containing at least one partial structure selected fromamong ether, aldehyde, ketone, ester, carbonate, acid anhydride, amideand imide, while the remaining R's are independently hydrogen orstraight, branched or cyclic alkyl groups of 1 to 15 carbon atoms.Examples of the monovalent hydrocarbon group of 2 to 15 carbon atomscontaining at least one partial structure selected from among ether,aldehyde, ketone, ester, carbonate, acid anhydride, amide and imideinclude methoxymethyl, methoxymethoxymethyl, formyl, methylcarbonyl,formyloxy, acetoxy, pivaloyloxy, formyloxymethyl, acetoxymethyl,pivaloyloxymethyl, methoxycarbonyl, 2-oxooxolan-3-yloxycarbonyl,4,4-dimethyl-2-oxooxolan-3-yloxycarbonyl,4-methyl-2-oxooxan-4-yloxycarbonyl,2-oxo-1,3-dioxolan-4-ylmethyloxycarbonyl, and5-methyl-2-oxooxolan-5-yloxycarbonyl. Examples of the straight, branchedor cyclic alkyl groups of 1 to 15 carbon atoms are the same asexemplified for R⁰⁰³.

R⁰¹⁰ to R⁰¹³, taken together, may form a ring, and in that event, atleast one of R⁰¹⁰ to R⁰¹³ is a divalent hydrocarbon group of 1 to 15carbon atoms containing at least one partial structure selected fromamong ether, aldehyde, ketone, ester, carbonate, acid anhydride, amideand imide, while the remaining R's are independently single bonds orstraight, branched or cyclic alkylene groups of 1 to 15 carbon atoms.Examples of the divalent hydrocarbon group of 1 to 15 carbon atomscontaining at least one partial structure selected from among ether,aldehyde, ketone, ester, carbonate, acid anhydride, amide and imideinclude 2-oxapropane-1,3-diyl, 1,1-dimethyl-oxapropane-1,3-diyl,1-oxo-2-oxapropane-1,3-diyl, 1,3-dioxo-2-oxapropane-1,3-diyl,1-oxo-2-oxabutane-1,4-diyl, and 1,3-dioxo-2-oxabutane-1,4-diyl, as wellas the groups exemplified as the monovalent hydrocarbon group of 1 to 15carbon atoms containing at least one partial structure selected fromamong ether, aldehyde, ketone, ester, carbonate, acid anhydride, amideand imide, with one hydrogen atom eliminated therefrom. Examples of thestraight, branched or cyclic alkylene groups of 1 to 15 carbon atomsinclude the groups exemplified for R⁰⁰³, with one hydrogen atomeliminated therefrom.

R⁰¹⁴ is a polycyclic hydrocarbon group having 7 to 15 carbon atoms or analkyl group containing a polycyclic hydrocarbon group, for example,norbornyl, bicyclo[3.3.1]-nonyl, tricyclo[5.2.1.0²⁶]decyl, adamantyl,ethyladamantyl, butyladamantyl, norbornylmethyl, and adamantylmethyl.

R⁰¹⁵ is an acid labile group, examples of which are the same asdescribed above. X is CH₂ or an oxygen atom. Letter k is equal to 0 or1.

The recurring units of formulae (M1) to (M8) are effective for impartingsuch desired properties as developer affinity, substrate adhesion andetching resistance to a resist composition based on a polymer comprisingthese recurring units. By adjusting the content of these recurringunits, the performance of the resist composition can be finely adjusted.

The polymers of the invention have a weight average molecular weight ofabout 1,000 to 500,000, and preferably about 3,000 to 100,000, asmeasured by gel permeation chromatography (GPC) using a polystyrenestandard. Outside the range, the etching resistance may become extremelylow and the resolution may become low because a substantial differencein rate of dissolution before and after exposure is lost.

The polymer of the invention can be prepared through copolymerizationreaction using a compound of the following general formula (1a) and/or(2a) as a first or first and second monomers, one, two or three membersselected from compounds of the following general formulae (3a) to (5a)as second to fourth or third to fifth monomers, and optionally, one ormore members selected from compounds of the following general formulae(M1a) to (M8a) as subsequent monomers:

Herein, k, p, R¹ to R⁹, Y and Z are as defined above:

Herein, k, R⁰⁰¹ to R⁰¹⁵, and X are as defined above.

By properly adjusting the proportion of the respective monomers used inthe copolymerization reaction, the polymer can be tailored so that itmay exert the preferred performance when blended in resist compositions.

In addition to (i) the monomer of formula (1a) and/or (2a), (ii) themonomer or monomers of formulas (3a) to (5a), and (iii) the monomer ormonomers of formulae (M1a) to (M8a), the polymer of the invention mayhave copolymerized therewith (iv) another monomer having acarbon-to-carbon double bond other than (i) to (iii). Examples of theadditional monomer (iv) include substituted acrylic acid esters such asmethyl methacrylate, methyl crotonate, dimethyl maleate, and dimethylitaconate, unsaturated carboxylic acids such as maleic acid, fumaricacid and itaconic acid, substituted or unsubstituted norbornenes such asnorbornene and methyl norbornene-5-carboxylate, and unsaturated acidanhydrides such as itaconic anhydride.

In the polymers of the invention, the preferred proportion of recurringunits based on the respective monomers is in the following range (in mol%), though not limited thereto.

(I) When the polymer is comprised of recurring units of formula (1)and/or (2) and recurring units of formula (3), it contains

(i) 1 to 90%, preferably 5 to 80%, and more preferably 10 to 70% ofrecurring units of formula (1) and/or (2) based on the monomer offormula (1a) and/or (2a),

(ii) 1 to 90%, preferably 5 to 80%, and more preferably 10 to 70% ofrecurring units of formula (3) based on the monomer of formula (3a),

(iii) 0 to 50%, preferably 0 to 40%, and more preferably 0 to 30% ofrecurring units of formula (M5) to (M8) based on the monomers of formula(M5a) to (M8a), and

(iv) 0 to 50%, preferably 0 to 40%, and more preferably 0 to 30% ofrecurring units based on another monomer.

(II) When the polymer is comprised of recurring units of formula (1)and/or (2), recurring units of formula (3) and recurring units offormula (4), it contains

(i) 1 to 49%, preferably 3 to 45%, and more preferably 5 to 40% ofrecurring units of formula (1) and/or (2) based on the monomer offormula (1a) and/or (2a),

(ii) 1 to 49%, preferably 3 to 45%, and more preferably 5 to 40% ofrecurring units of formula (3) based on the monomer of formula (3a),

(iii) 50 mol % of recurring units of formula (4) based on the monomer offormula (4a),

(iv) 0 to 25%, preferably 0 to 20%, and more preferably 0 to 15% ofrecurring units of formula (M5) to (M8) based on the monomers of formula(M5a) to (M8a), and

(v) 0 to 25%, preferably 0 to 20%, and more preferably 0 to 15% ofrecurring units based on another monomer.

(III) When the polymer is comprised of recurring units of formula (1)and/or (2), recurring units of formula (5) alone or in combination withrecurring units of formula (3), and recurring units of formula (4), itcontains

(i) 1 to 49%, preferably 3 to 45%, and more preferably 5 to 40% ofrecurring units of formula (1) and/or (2) based on the monomer offormula (1a) and/or (2a),

(ii) 0 to 40%, preferably 0 to 35%, and more preferably 0 to 30% ofrecurring units of formula (3) based on the monomer of formula (3a),

(iii) 1 to 80%, preferably 1 to 70%, and more preferably 1 to 50% ofrecurring units of formula (5) based on the monomer of formula (5a),

(iv) 1 to 49%, preferably 5 to 45%, and more preferably 10 to 40% ofrecurring units of formula (4) based on the monomer of formula (4a),

(v) 0 to 25%, preferably 0 to 20%, and more preferably 0 to 15% ofrecurring units of formula (M1) to (M8) based on the monomers of formula(M1a) to (M8a), and

(vi) 0 to 25%, preferably 0 to 20%, and more preferably 0 to 15% ofrecurring units based on another monomer.

A variety of copolymerization reaction methods may be used for thepreparation of the polymer according to the invention. The preferredpolymerization reaction is radical polymerization, anionicpolymerization or coordination polymerization.

For radical polymerization, preferred reaction conditions include (a) asolvent selected from among hydrocarbons such as benzene, ethers such astetrahydrofuran, alcohols such as ethanol, and ketones such as methylisobutyl ketone, (b) a polymerization initiator selected from azocompounds such as 2,2′-azobisisobutyronitrile and peroxides such asbenzoyl peroxide and lauroyl peroxide, (c) a temperature of about 0° C.to about 100° C., and (d) a time of about ½ hour to about 48 hours.Reaction conditions outside the described range may be employed ifdesired.

For anionic polymerization, preferred reaction conditions include (a) asolvent selected from among hydrocarbons such as benzene, ethers such astetrahydrofuran, and liquid ammonia, (b) a polymerization initiatorselected from metals such as sodium and potassium, alkyl metals such asn-butyllithium and sec-butyllithium, ketyl, and Grignard reagents, (c) atemperature of about −78° C. to about 0° C., (d) a time of about ½ hourto about 48 hours, and (e) a stopper selected from among proton-donativecompounds such as methanol, halides such as methyl iodide, andelectrophilic compounds. Reaction conditions outside the described rangemay be employed if desired.

For coordination polymerization, preferred reaction conditions include(a) a solvent selected from among hydrocarbons such as n-heptane andtoluene, (b) a catalyst such as, for example, Ziegler-Natta catalystscomprising a transition metal (e.g., titanium) and alkylaluminum, andPhillips catalysts of metal oxides having chromium or nickel compoundscarried thereon, (c) a temperature of about 0° C. to about 100° C., and(d) a time of about ½ hour to about 48 hours. Reaction conditionsoutside the described range may be employed if desired.

Resist Composition

Since the polymer of the invention is useful as the base resin of aresist composition, the other aspect of the invention provides a resistcomposition, especially a chemically amplified positive resistcomposition, comprising the polymer. Typically, the resist compositioncontains the polymer, a photoacid generator, and an organic solvent, andother optional components.

Photoacid Generator

The photoacid generator is a compound capable of generating an acid uponexposure to high energy radiation or electron beams and includes thefollowing:

(i) onium salts of the formula (P1a-1), (P1a-2) or (P1b),

(ii) diazomethane derivatives of the formula (P2),

(iii) glyoxime derivatives of the formula (P3),

(iv) bissulfone derivatives of the formula (P4),

(v) sulfonic acid esters of N-hydroxyimide compounds of the formula(P5),

(vi) β-ketosulfonic acid derivatives,

(vii) disulfone derivatives,

(viii) nitrobenzylsulfonate derivatives, and

(ix) sulfonate derivatives.

These photoacid generators are described in detail.

(i) Onium Salts of Formula (P1a-1), (P1a-2) or (P1b):

Herein, R^(101a), R^(101b), and R^(101c) independently representstraight, branched or cyclic alkyl, alkenyl, oxoalkyl or oxoalkenylgroups of 1 to 12 carbon atoms, aryl groups of 6 to 20 carbon atoms, oraralkyl or aryloxoalkyl groups of 7 to 12 carbon atoms, wherein some orall of the hydrogen atoms may be replaced by alkoxy or other groups.Also, R^(101b) and R^(101c), taken together, may form a ring. R^(101b)and R^(101c) each are alkylene groups of 1 to 6 carbon atoms when theyform a ring. K⁻ is a non-nucleophilic counter ion.

R^(101a), R^(101b), and R^(101c) may be the same or different and areillustrated below. Exemplary alkyl groups include methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl,cyclopentyl, cyclohexyl, cycloheptyl, cyclopropylmethyl,4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl.Exemplary alkenyl groups include vinyl, allyl, propenyl, butenyl,hexenyl, and cyclohexenyl. Exemplary oxoalkyl groups include2-oxocyclopentyl and 2-oxocyclohexyl as well as 2-oxopropyl,2-cyclopentyl-2-oxoethyl, 2-cyclohexyl-2-oxoethyl, and2-(4-methylcyclohexyl)-2-oxoethyl. Exemplary aryl groups include phenyland naphthyl; alkoxyphenyl groups such as p-methoxyphenyl,m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl; alkylnaphthyl groups such asmethylnaphthyl and ethylnaphthyl; alkoxynaphthyl groups such asmethoxynaphthyl and ethoxynaphthyl; dialkylnaphthyl groups such asdimethylnaphthyl and diethylnaphthyl; and dialkoxynaphthyl groups suchas dimethoxynaphthyl and diethoxynaphthyl. Exemplary aralkyl groupsinclude benzyl, phenylethyl, and phenethyl. Exemplary aryloxoalkylgroups are 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl,2-(1-naphthyl)-2-oxoethyl, and 2-(2-naphthyl)-2-oxoethyl. Examples ofthe non-nucleophilic counter ion represented by K⁻ include halide ionssuch as chloride and bromide ions, fluoroalkylsulfonate ions such astriflate, 1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate,arylsulfonate ions such as tosylate, benzenesulfonate,4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate, andalkylsulfonate ions such as mesylate and butanesulfonate.

Herein, R^(102a) and R^(102b) independently represent straight, branchedor cyclic alkyl groups of 1 to 8 carbon atoms. R¹⁰³ represents astraight, branched or cyclic alkylene group of 1 to 10 carbon atoms.R^(104a) and R^(104b) independently represent 2-oxoalkyl groups of 3 to7 carbon atoms. K⁻ is a non-nucleophilic counter ion.

Illustrative of the groups represented by R^(102a) and R^(102b) aremethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,pentyl, hexyl, heptyl, octyl, cyclopentyl, cyclohexyl,cyclopropylmethyl, 4-methylcyclohexyl, and cyclohexylmethyl.Illustrative of the groups represented by R¹⁰³ are methylene, ethylene,propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene,1,4-cyclohexylene, 1,2-cyclohexylene, 1,3-cyclopentylene,1,4-cyclooctylene, and 1,4-cyclohexanedimethylene. Illustrative of thegroups represented by R^(104a) and R^(104b) are 2-oxopropyl,2-oxocyclopentyl, 2-oxocyclohexyl, and 2-oxocycloheptyl. Illustrativeexamples of the counter ion represented by K⁻ are the same asexemplified for formulae (P1a-1) and (P1a-2).

(ii) Diazomethane Derivatives of Formula (P2):

Herein, R¹⁰⁵ and R¹⁰⁶ independently represent straight, branched orcyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms, arylor halogenated aryl groups of 6 to 20 carbon atoms, or aralkyl groups of7 to 12 carbon atoms.

Of the groups represented by R¹⁰⁵ and R¹⁰⁶, exemplary alkyl groupsinclude methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, pentyl, hexyl, heptyl, octyl, amyl, cyclopentyl, cyclohexyl,cycloheptyl, norbornyl, and adamantyl. Exemplary halogenated alkylgroups include trifluoromethyl, 1,1,1-trifluoroethyl,1,1,1-trichloroethyl, and nonafluorobutyl. Exemplary aryl groups includephenyl; alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl,o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; and alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tertbutylphenyl,4-butylphenyl, and dimethylphenyl. Exemplary halogenated aryl groupsinclude fluorophenyl, chlorophenyl, and 1,2,3,4,5-pentafluorophenyl.Exemplary aralkyl groups include benzyl and phenethyl.

(iii) Glyoxime Derivatives of Formula (P3):

Herein, R¹⁰⁷ R¹⁰⁸, and R¹⁰⁹ independently represent straight, branchedor cyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms,aryl or halogenated aryl groups of 6 to 20 carbon atoms, or aralkylgroups of 7 to 12 carbon atoms. Also, R¹⁰⁸ and R¹⁰⁹, taken together, mayform a ring. R¹⁰⁸ and R¹⁰⁹ each are straight or branched alkylene groupsof 1 to 6 carbon atoms when they form a ring.

Illustrative examples of the alkyl, halogenated alkyl, aryl, halogenatedaryl, and aralkyl groups represented by R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ are thesame as exemplified for R¹⁰⁵ and R¹⁰⁶. Examples of the alkylene groupsrepresented by R¹⁰⁸ and R¹⁰⁹ include methylene, ethylene, propylene,butylene, and hexylene.

(iv) Bissulfone Derivatives of Formula (P4):

Herein, R^(101a) and R^(101b) are as defined above.

(v) Sulfonic Acid Esters of N-hydroxyimide Compounds of Formula (P5):

Herein, R¹¹⁰ is an arylene group of 6 to 10 carbon atoms, alkylene groupof 1 to 6 carbon atoms, or alkenylene group of 2 to 6 carbon atomswherein some or all of the hydrogen atoms may be replaced by straight orbranched alkyl or alkoxy groups of 1 to 4 carbon atoms, nitro, acetyl,or phenyl groups. R¹¹¹ is a straight, branched or cyclic alkyl group of1 to 8 carbon atoms, alkenyl, alkoxyalkyl, phenyl or naphthyl groupwherein some or all of the hydrogen atoms may be replaced by alkyl oralkoxy groups of 1 to 4 carbon atoms, phenyl groups (which may havesubstituted thereon an alkyl or alkoxy of 1 to 4 carbon atoms, nitro, oracetyl group), hetero-aromatic groups of 3 to 5 carbon atoms, orchlorine or fluorine atoms.

Of the groups represented by R¹¹⁰, exemplary arylene groups include1,2-phenylene and 1,8-naphthylene; exemplary alkylene groups includemethylene, ethylene, trimethylene, tetramethylene, phenylethylene, andnorbornane-2,3-diyl; and exemplary alkenylene groups include1,2-vinylene, 1-phenyl-1,2-vinylene, and 5-norbornene-2,3-diyl. Of thegroups represented by R¹¹¹, exemplary alkyl groups are as exemplifiedfor R^(101a) to R^(101c); exemplary alkenyl groups include vinyl,1-propenyl, allyl, 1-butenyl, 3-butenyl, isoprenyl, 1-pentenyl,3-pentenyl, 4-pentenyl, dimethylallyl, 1-hexenyl, 3-hexenyl, 5-hexenyl,1-heptenyl, 3-heptenyl, 6-heptenyl, and 7-octenyl; and exemplaryalkoxyalkyl groups include methoxymethyl, ethoxymethyl, propoxymethyl,butoxymethyl, pentyloxymethyl, hexyloxymethyl, heptyloxymethyl,methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl, pentyloxyethyl,hexyloxyethyl, methoxypropyl, ethoxypropyl, propoxypropyl, butoxypropyl,methoxybutyl, ethoxybutyl, propoxybutyl, methoxypentyl, ethoxypentyl,methoxyhexyl, and methoxyheptyl.

Of the substituents on these groups, the alkyl groups of 1 to 4 carbonatoms include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl andtert-butyl; the alkoxy groups of 1 to 4 carbon atoms include methoxy,ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, and tert-butoxy; thephenyl groups which may have substituted thereon an alkyl or alkoxy of 1to 4 carbon atoms, nitro, or acetyl group include phenyl, tolyl,p-tert-butoxyphenyl, p-acetylphenyl and p-nitrophenyl; thehetero-aromatic groups of 3 to 5 carbon atoms include pyridyl and furyl.

Illustrative examples of the photoacid generator include:

onium salts such as diphenyliodonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)phenyliodonium trifluoromethanesulfonate,diphenyliodonium p-toluenesulfonate, (p-tert-butoxyphenyl)phenyliodoniump-toluenesulfonate, triphenylsulfonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,bis(p-tert-butoxyphenyl)phenylsulfonium trifluoromethanesulfonate,tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,triphenylsulfonium p-toluenesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,bis(p-tert-butoxyphenyl)phenylsulfonium p-toluenesulfonate,tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,triphenylsulfonium nonafluorobutanesulfonate, triphenylsulfoniumbutanesulfonate, trimethylsulfonium trifluoromethanesulfonate,trimethylsulfonium p-toluenesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium p-toluenesulfonate,dimethylphenylsulfonium trifluoromethanesulfonate,dimethylphenylsulfonium p-toluenesulfonate, dicyclohexylphenylsulfoniumtrifluoromethanesulfonate, dicyclohexylphenylsulfoniump-toluenesulfonate, trinaphthylsulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,(2-norbornyl)methyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,ethylenebis[methyl(2-oxocyclopentyl)sulfoniumtrifluoromethanesulfonate], and1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;

diazomethane derivatives such as bis(benzenesulfonyl)diazomethane,bis(p-toluenesulfonyl)diazomethane, bis(xylenesulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(cyclopentylsulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane,bis(isobutylsulfonyl)diazomethane, bis(sec-butylsulfonyl)diazomethane,bis(n-propylsulfonyl)diazomethane, bis(isopropylsulfonyl)diazomethane,bis(tert-butylsulfonyl)diazomethane, bis(n-amylsulfonyl)diazomethane,bis(isoamylsulfonyl)diazomethane, bis(sec-amylsulfonyl)diazomethane,bis(tert-amylsulfonyl)diazomethane,1-cyclohexylsulfonyl-1-(tert-butylsulfonyl)diazomethane,1-cyclohexylsulfonyl-1-(tert-amylsulfonyl)diazomethane, and1-tert-amylsulfonyl-1-(tert-butylsulfonyl)diazomethane;

glyoxime derivatives such asbis-O-(p-toluenesulfonyl)-α-dimethylglyoxime,bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)-α-dimethylglyoxime,bis-O-(n-butanesulfonyl)-α-diphenylglyoxime,bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime,bis-O-(n-butanesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-O-(methanesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,bis-O-(1,1,1-trifluoroethanesulfonyl)-α-dimethylglyoxime,bis-O-(tert-butanesulfonyl)-α-dimethylglyoxime,bis-O-(perfluorooctanesulfonyl)-α-dimethylglyoxime,bis-O-(cyclohexanesulfonyl)-α-dimethylglyoxime,bis-O-(benzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-tert-butyl-benzenesulfonyl)-α-dimethylglyoxime,bis-O-(xylenesulfonyl)-α-dimethylglyoxime, andbis-O-(camphorsulfonyl)-α-dimethylglyoxime;

bissulfone derivatives such as bisnaphthylsulfonylmethane,bistrifluoromethylsulfonylmethane, bismethylsulfonylmethane,bisethylsulfonylmethane, bispropylsulfonylmethane,bisisopropylsulfonylmethane, bis-p-toluenesulfonylmethane, andbisbenzenesulfonylmethane;

β-ketosulfone derivatives such as2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane and2-isopropylcarbonyl-2-(p-toluenesulfonyl)propane;

disulfone derivatives such as diphenyl disulfone and dicyclohexyldisulfone;

nitrobenzyl sulfonate derivatives such as 2,6-dinitrobenzylp-toluenesulfonate and 2,4-dinitrobenzyl p-toluenesulfonate;

sulfonic acid ester derivatives such as1,2,3-tris-methanesulfonyloxy)benzene,1,2,3-tris(trifluoromethanesulfonyloxy)benzene, and1,2,3-tris(p-toluenesulfonyloxy)benzene; and

sulfonic acid esters of N-hydroxyimides such as N-hydroxysuccinimidemethanesulfonate, N-hydroxysuccinimide trifluoromethanesulfonate,N-hydroxysuccinimide ethanesulfonate, N-hydroxysuccinimide1-propanesulfonate, N-hydroxysuccinimide 2-propanesulfonate,N-hydroxysuccinimide 1-pentanesulfonate, N-hydroxysuccinimide1-octanesulfonate, N-hydroxysuccinimide p-toluenesulfonate,N-hydroxysuccinimide p-methoxybenzenesulfonate, N-hydroxysuccinimide2-chloroethanesulfonate, N-hydroxysuccinimide benzenesulfonate,N-hydroxysuccinimide 2,4,6-trimethylbenzenesulfonate,N-hydroxysuccinimide 1-naphthalenesulfonate, N-hydroxysuccinimide2-naphthalenesulfonate, N-hydroxy-2-phenylsuccinimide methanesulfonate,N-hydroxymaleimide methanesulfonate, N-hydroxymaleimide ethanesulfonate,N-hydroxy-2-phenylmaleimide methanesulfonate, N-hydroxyglutarimidemethanesulfonate, N-hydroxyglutarimide benzenesulfonate,N-hydroxyphthalimide methanesulfonate, N-hydroxyphthalimidebenzenesulfonate, N-hydroxyphthalimide trifluoromethanesulfonate,N-hydroxyphthalimide p-toluenesulfonate, N-hydroxynaphthalimidemethanesulfonate, N-hydroxynaphthalimide benzenesulfonate,N-hydroxy-5-norbornene-2,3-dicarboxyimide methanesulfonate,N-hydroxy-5-norbornene-2,3-dicarboxyimide trifluoromethanesulfonate, andN-hydroxy-5-norbornene-2,3-dicarboxyimide p-toluenesulfonate.

Preferred among these photoacid generators are onium salts such astriphenylsulfonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,triphenylsulfonium p-toluenesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,trinaphthylsulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,(2-norbornyl)methyl(2-oxocylohexyl)sulfonium trifluoromethanesulfonate,and 1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;diazomethane derivatives such as bis(benzenesulfonyl)diazomethane,bis(p-toluenesulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane,bis(n-butylsulfonyl)diazomethane, bis(isobutylsulfonyl)diazomethane,bis(sec-butylsulfonyl)diazomethane, bis(n-propylsulfonyl)diazomethane,bis(isopropylsulfonyl)diazomethane, andbis(tert-butylsulfonyl)diazomethane; glyoxime derivatives such asbis-O-(p-toluenesulfonyl)-α-dimethylglyoxime andbis-O-(n-butanesulfonyl)-α-dimethylglyoxime; bissulfone derivatives suchas bisnaphthylsulfonylmethane; and sulfonic acid esters ofN-hydroxyimide compounds such as N-hydroxysuccinimide methanesulfonate,N-hydroxysuccinimide trifluoromethanesulfonate, N-hydroxysuccinimide1-propanesulfonate, N-hydroxysuccinimide 2-propanesulfonate,N-hydroxysuccinimide 1-pentanesulfonate, N-hydroxysuccinimidep-toluenesulfonate, N-hydroxynaphthalimide methanesulfonate, andN-hydroxynaphthalimide benzenesulfonate.

These photoacid generators may be used singly or in combinations of twoor more thereof. Onium salts are effective for improving rectangularity,while diazomethane derivatives and glyoxime derivatives are effectivefor reducing standing waves. The combination of an onium salt with adiazomethane or a glyoxime derivative allows for fine adjustment of theprofile.

The photoacid generator is added in an amount of 0.1 to 15 parts, andespecially 0.5 to 8 parts by weight, per 100 parts by weight of the baseresin (all parts are by weight, hereinafter). Less than 0.1 part of thephotoacid generator would provide a poor sensitivity whereas more than15 parts of the photoacid generator would adversely affect transparencyand resolution.

Organic Solvent

The organic solvent used herein may be any organic solvent in which thebase resin, photoacid generator, and other components are soluble.Illustrative, non-limiting, examples of the organic solvent includeketones such as cyclohexanone and methyl-2-n-amylketone; alcohols suchas 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol,and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethylether, ethylene glycol monomethyl ether, propylene glycol monoethylether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether,and diethylene glycol dimethyl ether; and esters such as propyleneglycol monomethyl ether acetate, propylene glycol monoethyl etheracetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate. These solvents may be used alone or in combinations of two ormore thereof. Of the above organic solvents, it is recommended to usediethylene glycol dimethyl ether and 1-ethoxy-2-propanol because thephotoacid generator is most soluble therein, propylene glycol monomethylether acetate because it is a safe solvent, or a mixture thereof.

An appropriate amount of the organic solvent used is about 200 to 1,000parts, especially about 400 to 800 parts by weight per 100 parts byweight of the base resin.

Other Polymer

To the resist composition of the invention, another polymer other thanthe inventive polymer comprising recurring units of formula (1) and/or(2) may also be added. The other polymers that can be added to theresist composition are, for example, those polymers comprising units ofthe following formula (R1) and/or (R2) and having a weight averagemolecular weight of about 1,000 to about 500,000, especially about 5,000to about 100,000 although the other polymers are not limited thereto:

Herein, R⁰⁰¹ is hydrogen, methyl or CH₂CO₂R⁰⁰³. R⁰⁰² is hydrogen, methylor CO₂R⁰⁰³. R⁰⁰³ is a straight, branched or cyclic alkyl group of 1 to15 carbon atoms. R⁰⁰⁴ is hydrogen or a monovalent hydrocarbon group of 1to 15 carbon atoms having a carboxyl or hydroxyl group. At least one ofR⁰⁰⁵ to R⁰⁰⁸ represents a monovalent hydrocarbon group of 1 to 15 carbonatoms having a carboxyl or hydroxyl group while the remaining R'sindependently represent hydrogen or a straight, branched or cyclic alkylgroup of 1 to 15 carbon atoms. Alternatively, R⁰⁰⁵ to R⁰⁰⁸, takentogether, may form a ring, and in that event, at least one of R⁰⁰⁵ toR⁰⁰⁸ is a divalent hydrocarbon group of 1 to 15 carbon atoms having acarboxyl or hydroxyl group, while the remaining R's are independentlysingle bonds or straight, branched or cyclic alkylene groups of 1 to 15carbon atoms. R⁰⁰⁹ is a monovalent hydrocarbon group of 2 to 15 carbonatoms containing at least one partial structure selected from amongether, aldehyde, ketone, ester, carbonate, acid anhydride, amide andimide. At least one of R⁰¹⁰ to R⁰¹³ is a monovalent hydrocarbon group of2 to 15 carbon atoms containing at least one partial structure selectedfrom among ether, aldehyde, ketone, ester, carbonate, acid anhydride,amide and imide, while the remaining R's are independently hydrogen orstraight, branched or cyclic alkyl groups of 1 to 15 carbon atoms. R⁰¹⁰to R⁰¹³, taken together, may form a ring, and in that event, at leastone of R⁰¹⁰ to R⁰¹³ is a divalent hydrocarbon group of 1 to 15 carbonatoms containing at least one partial structure selected from amongether, aldehyde, ketone, ester, carbonate, acid anhydride, amide andimide, while the remaining R's are independently single bonds orstraight, branched or cyclic alkylene groups of 1 to 15 carbon atoms.R⁰¹⁴ is a polycyclic hydrocarbon group having 7 to 15 carbon atoms or analkyl group containing a polycyclic hydrocarbon group. R⁰¹⁵ is an acidlabile group. R⁰¹⁶ is hydrogen or methyl. R⁰¹⁷ is a straight, branchedor cyclic alkyl group of 1 to 8 carbon atoms. X is CH₂ or an oxygenatom. Letter k′ is equal to 0 or 1; a1′, a2′, a3′, b1′, b2′, b3′, c1′,c2′, c3′, d1′, d2′, d3′, and e′ are numbers from 0 to less than 1,satisfying a1′+a2′+a3′+b1′+b2′+b3′+c1′+c2′+c3′+d1′+d2′+d3′+e′=1; f′, g′,h′, i′, and j′ are numbers from 0 to less than 1, satisfyingf′+g′+h′+i′+j′=1; x′, y′ and z′ each are an integer of 0 to 3,satisfying 1≦x′+y′+z′≦5 and 1≦y′+z′≦3.

Exemplary groups of these R's are as exemplified above.

The inventive polymer (comprising recurring units of formula (1) and/or(2)) and the other polymer are preferably blended in a weight ratio from100:0 to 10:90, more preferably from 100:0 to 20:80. If the blend ratioof the inventive polymer is below this range, the resist compositionwould become poor in some of the desired properties. The properties ofthe resist composition can be adjusted by properly changing the blendratio of the inventive polymer.

The other polymer is not limited to one type and a mixture of two ormore other polymers may be added. The use of plural polymers allows foreasy adjustment of resist properties.

Dissolution Regulator

To the resist composition, a dissolution regulator may be added. Thedissolution regulator is a compound having on the molecule at least twophenolic hydroxyl groups, in which an average of from 0 to 100 mol % ofall the hydrogen atoms on the phenolic hydroxyl groups are replaced withacid labile groups or a compound having on the molecule at least onecarboxyl group, in which an average of 50 to 100 mol % of all thehydrogen atoms on the carboxyl groups are replaced with acid labilegroups, both the compounds having an average molecular weight within arange of 100 to 1,000, and preferably 150 to 800.

The degree of substitution of the hydrogen atoms on the phenolichydroxyl groups with acid labile groups is on average at least 0 mol %,and preferably at least 30 mol %, of all the phenolic hydroxyl groups.The upper limit is 100 mol %, and preferably 80 mol %. The degree ofsubstitution of the hydrogen atoms on the carboxyl groups with acidlabile groups is on average at least 50 mol %, and preferably at least70 mol %, of all the carboxyl groups, with the upper limit being 100 mol%.

Preferable examples of such compounds having two or more phenolichydroxyl groups or compounds having at least one carboxyl group includethose of formulas (D1) to (D14) below:

In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straight orbranched alkyl or alkenyl of 1 to 8 carbon atoms; R²⁰³ is hydrogen, astraight or branched alkyl or alkenyl of 1 to 8 carbon atoms, or—(R²⁰⁷)_(h)—COOH; R²⁰⁴ is —(CH₂)_(i)— (where i=2 to 10), an arylene of 6to 10 carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfuratom; R²⁰⁵ is an alkylene of 1 to 10 carbon atoms, an arylene of 6 to 10carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R²⁰⁶is hydrogen, a straight or branched alkyl or alkenyl of 1 to 8 carbonatoms, or a hydroxyl-substituted phenyl or naphthyl; R²⁰⁷ is a straightor branched alkylene of 1 to 10 carbon atoms; R²⁰⁸ is hydrogen orhydroxyl; the letter j is an integer from 0 to 5; u and h are each 0 or1; s, t, s′, t′, s″, and t″ are each numbers which satisfy s+t=8,s′+t′=5, and s″+t″=4, and are such that each phenyl skeleton has atleast one hydroxyl group; and α is a number such that the compounds offormula (D8) or (D9) have a molecular weight of from 100 to 1,000.

In the above formulas, suitable examples of R²⁰¹ and R²⁰² includehydrogen, methyl, ethyl, butyl, propyl, ethynyl, and cyclohexyl;suitable examples of R²⁰³ include the same groups as for R²⁰¹ and R²⁰²,as well as —COOH and —CH₂COOH; suitable examples of R²⁰⁴ includeethylene, phenylene, carbonyl, sulfonyl, oxygen, and sulfur; suitableexamples of R²⁰⁵ include methylene as well as the same groups as forR²⁰⁴; and suitable examples of R²⁰⁶ include hydrogen, methyl, ethyl,butyl, propyl, ethynyl, cyclohexyl, and hydroxyl-substituted phenyl ornaphthyl.

Exemplary acid labile groups on the dissolution regulator include groupsof the following general formulae (L1) to (L4), tertiary alkyl groups of4 to 20 carbon atoms, trialkylsilyl groups in which each of the alkylshas 1 to 6 carbon atoms, and oxoalkyl groups of 4 to 20 carbon atoms:

In these formulas, R^(L01) and R^(L02) are each hydrogen or a straight,branched or cyclic alkyl having 1 to 18 carbon atoms; and R^(L03) is amonovalent hydrocarbon group of 1 to 18 carbon atoms which may contain aheteroatom (e.g., oxygen). A pair of R^(L01) and R^(L02), a pair ofR^(L01) and R^(L03) or a pair of R^(L02) and R^(L03) may together form aring, with the proviso that R^(L01), R^(L02) ₁ and R^(L03) are each astraight or branched alkylene of 1 to 18 carbon atoms when they form aring. R^(L04) is a tertiary alkyl group of 4 to 20 carbon atoms, atrialkysilyl group in which each of the alkyls has 1 to 6 carbon atoms,an oxoalkyl group of 4 to 20 carbon atoms, or a group of the formula(L1). R^(L05) is a monovalent hydrocarbon groups of 1 to 8 carbon atomswhich may contain a hetero atom or a substituted or unsubstituted arylgroup of 6 to 20 carbon atoms. R^(L06) is a monovalent hydrocarbongroups of 1 to 8 carbon atoms which may contain a hetero atom or asubstituted or unsubstituted aryl group of 6 to 20 carbon atoms. R^(L07)to R^(L16) independently represent hydrogen or monovalent hydrocarbongroups of 1 to 15 carbon atoms which may contain a hetero atom.Alternatively, R^(L07) to R^(L16), taken together, may form a ring. Eachof R^(L07) to R^(L16) represents a divalent C₁-C₁₅ hydrocarbon groupwhich may contain a hetero atom, when they form a ring. Two of R^(L07)to R^(L16) which are attached to adjoining carbon atoms may bondtogether directly to form a double bond. Letter y is an integer of 0 to6. Letter m is equal to 0 or 1, n is equal to 0, 1, 2 or 3, and 2m+n isequal to 2 or 3. Illustrative examples of these groups are as previouslyexemplified.

The dissolution regulator may be formulated in an amount of 0 to 50parts, preferably 0 to 40 parts, and more preferably 0 to 30 parts, per100 parts of the base resin, and may be used singly or as a mixture oftwo or more thereof. The use of more than 50 parts would lead toslimming of the patterned film, and thus a decline in resolution.

The dissolution regulator can be synthesized by introducing acid labilegroups into a compound having phenolic hydroxyl or carboxyl groups inaccordance with an organic chemical formulation.

Basic Compound

In the resist composition of the invention, a basic compound may beblended. A suitable basic compound used herein is a compound capable ofsuppressing the rate of diffusion when the acid generated by thephotoacid generator diffuses within the resist film. The inclusion ofthis type of basic compound holds down the rate of acid diffusion withinthe resist film, resulting in better resolution. In addition, itsuppresses changes in sensitivity following exposure, thus reducingsubstrate and environment dependence, as well as improving the exposurelatitude and the pattern profile.

Examples of basic compounds include primary, secondary, and tertiaryaliphatic amines, mixed amines, aromatic amines, heterocyclic amines,carboxyl group-bearing nitrogenous compounds, sulfonyl group-bearingnitrogenous compounds, hydroxyl group-bearing nitrogenous compounds,hydroxyphenyl group-bearing nitrogenous compounds, alcoholic nitrogenouscompounds, amide derivatives, and imide derivatives.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,iso-butylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine,di-iso-propylamine, di-n-butylamine, di-iso-butylamine,di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine,dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine,didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine,tri-iso-butylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,1-methyl-2-pyridone, 4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine,2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine),pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives,pyrazoline derivatives, pyrazolidine derivatives, piperidinederivatives, piperazine derivatives, morpholine derivatives, indolederivatives, isoindole derivatives, 1H-indazole derivatives, indolinederivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable carboxyl group-bearing nitrogenous compoundsinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable sulfonyl group-bearing nitrogenous compounds include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable hydroxyl group-bearing nitrogenous compounds, hydroxyphenylgroup-bearing nitrogenous compounds, and alcoholic nitrogenous compoundsinclude 2-hydroxypyridine, aminocresol, 2,4-quinolinediol,3-indolemethanol hydrate, monoethanolamine, diethanolamine,triethanolamine, N-ethyldiethanolamine, N,N-diethylethanolamine,triisopropanolamine, 2,2′-iminodiethanol, 2-aminoethanol,3-amino-1-propanol, 4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine,2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine,1-[2-(2-hydroxyethoxy)ethyl]-piperazine, piperidine ethanol,1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone,3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol,8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidineethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, andN-(2-hydroxyethyl)isonicotinamide. Examples of suitable amidederivatives include formamide, N-methylformamide, N,N-dimethylformamide,acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, andbenzamide. Suitable imide derivatives include phthalimide, succinimide,and maleimide.

In addition, basic compounds of the following general formula (B1) mayalso be included alone or in admixture:

N(X)_(n)(Y)_(3−n)  B1

In the formula, n is equal to 1, 2 or 3; Y is independently hydrogen ora straight, branched or cyclic alkyl group of 1 to 20 carbon atoms whichmay contain a hydroxyl group or ether; and X is independently selectedfrom groups of the following general formulas (X1) to (X3), and two orthree X's may bond together to form a ring

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight orbranched alkylene groups of 1 to 4 carbon atoms; R³⁰¹, R³⁰⁴ and R³⁰⁶ areindependently hydrogen, straight, branched or cyclic alkyl groups of 1to 20 carbon atoms, which may contain at least one hydroxyl group,ether, ester or lactone ring; and R³⁰³ is a single bond or a straight orbranched alkylene group of 1 to 4 carbon atoms.

Illustrative examples of the compounds of formula (B1) includetris(2-methoxymethoxyethyl)amine, tris{2-(methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15-crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine,tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine,tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine,tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy—propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andβ-(diethylamino)-δ-valerolactone.

Also useful are one or more of cyclic structure-bearing basic compoundshaving the following general formula (B2):

Herein X is as defined above, and R³⁰⁷ is a straight or branchedalkylene group of 2 to 20 carbon atoms which may contain one or morecarbonyl groups, ether structures, ester structures or sulfidestructures.

Illustrative examples of the cyclic structure-bearing basic compoundshaving formula (B2) include

1-[2-(methoxymethoxy)ethyl]pyrrolidine,

1-[2-(methoxymethoxy)ethyl]piperidine,

4-[2-(methoxymethoxy)ethyl]morpholine,

1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine,

1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine,

4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine,

2-(1-pyrrolidinyl)ethyl acetate,

2-piperidinoethyl acetate,

2-morpholinoethyl acetate,

2-(1-pyrrolidinyl)ethyl formate,

2-piperidinoethyl propionate,

2-morpholinoethyl acetoxyacetate,

2-(1-pyrrolidinyl)ethyl methoxyacetate,

4-[2-(methoxycarbonyloxy)ethyl]morpholine,

1-[2-(t-butoxycarbonyloxy)ethyl]piperidine,

4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine,

methyl 3-(1-pyrrolidinyl)propionate,

methyl 3-piperidinopropionate,

methyl 3-morpholinopropionate,

methyl 3-(thiomorpholino)propionate,

methyl 2-methyl-3-(1-pyrrolidinyl)propionate,

ethyl 3-morpholinopropionate,

methoxycarbonylmethyl 3-piperidinopropionate,

2-hydroxyethyl 3-(1-pyrrolidinyl)propionate,

2-acetoxyethyl 3-morpholinopropionate,

2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate,

tetrahydrofurfuryl 3-morpholinopropionate,

glycidyl 3-piperidinopropionate,

2-methoxyethyl 3-morpholinopropionate,

2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate,

butyl 3-morpholinopropionate,

cyclohexyl 3-piperidinopropionate,

α-(1-pyrrolidinyl)methyl-γ-butyrolactone,

β-piperidino-γ-butyrolactone,

β-morpholino-δ-valerolactone,

methyl 1-pyrrolidinylacetate,

methyl piperidinoacetate,

methyl morpholinoacetate,

methyl thiomorpholinoacetate,

ethyl 1-pyrrolidinylacetate, and

2-methoxyethyl morpholinoacetate.

Also, one or more of cyano-bearing basic compounds having the followinggeneral formulae (B3) to (B6) may be blended:

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ each areindependently a straight or branched alkylene group of 1 to 4 carbonatoms.

Illustrative examples of the cyano-bearing basic compounds havingformulae (B3) to (B6) include

3-(diethylamino)propiononitrile,

N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile,

N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile,

N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile,

N,N-bis(2-methoxyethyl)-3-aminopropiononitrile,

N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile,

methyl N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate,

methyl N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate,

methyl N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate,

N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile,

N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile,

N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,

N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile,

N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile,

N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile,

N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile,

N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,

N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile,

N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile,

N,N-bis(2-cyanoethyl)-3-aminopropiononitrile,

diethylaminoacetonitrile,

N,N-bis(2-hydroxyethyl)aminoacetonitrile,

N,N-bis(2-acetoxyethyl)aminoacetonitrile,

N,N-bis(2-formyloxyethyl)aminoacetonitrile,

N,N-bis(2-methoxyethyl)aminoacetonitrile,

N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile,

methyl N-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate,

methyl N-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate,

methyl N-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate,

N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile,

N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile,

N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile,

N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile,

N-cyanomethyl-N-[2-(methoxymethoxy)ethyl]aminoacetonitrile,

N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile,

N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile,

N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile,

N,N-bis(cyanomethyl)aminoacetonitrile,

1-pyrrolidinepropiononitrile,

1-piperidinepropiononitrile,

4-morpholinepropiononitrile,

1-pyrrolidineacetonitrile,

1-piperidineacetonitrile,

4-morpholineacetonitrile,

cyanomethyl 3-diethylaminopropionate,

cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate,

cyanomethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate,

cyanomethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate,

cyanomethyl N,N-bis(2-methoxyethyl)-3-aminopropionate,

cyanomethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate,

2-cyanoethyl 3-diethylaminopropionate,

2-cyanoethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate,

2-cyanoethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate,

2-cyanoethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate,

2-cyanoethyl N,N-bis(2-methoxyethyl)-3-aminopropionate,

2-cyanoethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate,

cyanomethyl 1-pyrrolidinepropionate,

cyanomethyl 1-piperidinepropionate,

cyanomethyl 4-morpholinepropionate,

2-cyanoethyl 1-pyrrolidinepropionate,

2-cyanoethyl 1-piperidinepropionate, and

2-cyanoethyl 4-morpholinepropionate.

The basic compound is preferably formulated in an amount of 0.001 to 10parts, and especially 0.01 to 1 part, per part of the photoacidgenerator. Less than 0.001 part of the basic compound may fail toachieve the desired effects thereof, while the use of more than 10 partswould result in too low a sensitivity and resolution.

Other Components

In the resist composition, a compound bearing a ≡C—COOH group in amolecule may be blended. Exemplary, non-limiting compounds bearing a≡C—COOH group are one or more compounds selected from Groups I and IIbelow. Including this compound improves the PED stability of the resistand ameliorates edge roughness on nitride film substrates.

Group I

Compounds in which some or all of the hydrogen atoms on the phenolichydroxyl groups of the compounds of general formulas (A1) to (A10) belowhave been replaced with —R⁴⁰¹—COOH (wherein R⁴⁰¹ is a straight orbranched alkylene of 1 to 10 carbon atoms), and in which the molar ratioC/(C+D) of phenolic hydroxyl groups (C) to ≡C—COOH groups (D) in themolecule is from 0.1 to 1.0:

In these formulas, R⁴⁰⁸ is hydrogen or methyl; R⁴⁰² and R⁴⁰³ are eachhydrogen or a straight or branched alkyl or alkenyl of 1 to 8 carbonatoms; R⁴⁰⁴ is hydrogen, a straight or branched alkyl or alkenyl of 1 to8 carbon atoms, or a —(R⁴⁰⁹)_(h)—COOR′ group (R′ being hydrogen or—R⁴⁰⁹—COOH); R⁴⁰⁵ is —(CH₂)_(i)— (wherein i is 2 to 10), an arylene of 6to 10 carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfuratom; R⁴⁰⁶ is an alkylene of 1 to 10 carbon atoms, an arylene of 6 to 10carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R⁴⁰⁷is hydrogen, a straight or branched alkyl or alkenyl of 1 to 8 carbonatoms, or a hydroxyl-substituted phenyl or naphthyl; R⁴⁰⁹ is a straightor branched alkylene of 1 to 10 carbon atoms; R⁴¹⁰ is hydrogen, astraight or branched alkyl or alkenyl of 1 to 8 carbon atoms, or a—R⁴¹¹—COOH group; R⁴¹¹ is a straight or branched alkylene of 1 to 10carbon atoms; the letter j is an integer from 0 to 5; u and h are each 0or 1; s1, t1, s2, t2, s3, t3, s4, and t4 are each numbers which satisfys1+t1=8, s2+t2=5, s3+t3=4, and s4+t4=6, and are such that each phenylskeleton has at least one hydroxyl group; κ is a number such that thecompound of formula (A6) may have a weight average molecular weight of1,000 to 5,000; and λ is a number such that the compound of formula (A7)may have a weight average molecular weight of 1,000 to 10,000.

Group II

Compounds of general formulas (A11) to (A15) below.

In these formulas, R⁴⁰², R⁴⁰³, and R⁴¹¹ are as defined above; R⁴¹² ishydrogen or hydroxyl; s5 and t5 are numbers which satisfy s5≧0, t5≧0,and s5+t5=5; and h′ is equal to 0 or 1.

Illustrative, non-limiting examples of the compound bearing a ≡C—COOHgroup include compounds of the general formulas AI-1 to AI-14 and AII-1to AII-10 below:

In the above formulas, R″ is hydrogen or a CH₂COOH group such that theCH₂COOH group accounts for 10 to 100 mol % of R″ in each compound, α andκ are as defined above:

The compound bearing a ≡C—COOH group within the molecule may be usedsingly or as combinations of two or more thereof.

The compound bearing a ≡C—COOH group within the molecule is added in anamount ranging from 0 to 5 parts, preferably 0.1 to 5 parts, morepreferably 0.1 to 3 parts, further preferably 0.1 to 2 parts, per 100parts of the base resin. More than 5 parts of the compound can reducethe resolution of the resist composition.

The resist composition of the invention may additionally include anacetylene alcohol derivative for the purpose of enhancing the shelfstability. Preferred acetylene alcohol derivatives are those having thegeneral formula (S1) or (S2) below:

In the formulas, R⁵⁰¹, R⁵⁰², R⁵⁰³, R⁵⁰⁴ and R⁵⁰⁵ are each hydrogen or astraight, branched, or cyclic alkyl of 1 to 8 carbon atoms; and X and Yare each 0 or a positive number, satisfying 0≦X≦30, 0≦Y≦30, and0≦X+Y≦40.

Preferable examples of the acetylene alcohol derivative include Surfynol61, Surfynol 82, Surfynol 104, Surfynol 104E, Surfynol 104H, Surfynol104A, Surfynol TG, Surfynol PC, Surfynol 440, Surfynol 465, and Surfynol485 from Air Products and Chemicals Inc., and Surfynol E1004 fromNisshin Chemical Industry K.K.

The acetylene alcohol derivative is preferably added in an amount of0.01 to 2% by weight, and more preferably 0.02 to 1% by weight, per 100%by weight of the resist composition. Less than 0.01% by weight would beineffective for improving coating characteristics and shelf stability,whereas more than 2% by weight would result in a resist having a lowresolution.

The resist composition of the invention may include optionalingredients, for example, a surfactant which is commonly used forimproving the coating characteristics. Optional ingredients may be addedin conventional amounts so long as this does not compromise the objectsof the invention.

Nonionic surfactants are preferred, examples of which includeperfluoroalkylpolyoxyethylene ethanols, fluorinated alkyl esters,perfluoroalkylamine oxides, perfluoroalkyl EO-addition products, andfluorinated organosiloxane compounds. Useful surfactants arecommercially available under the trade names Florade FC-430 and FC-431from Sumitomo 3M, Ltd., Surflon S-141 and S-145, KH-10, KH-20, KH-30 andKH-40 from Asahi Glass Co., Ltd., Unidyne DS-401, DS-403 and DS-451 fromDaikin Industry Co., Ltd., Megaface F-8151 from Dai-Nippon Ink &Chemicals, Inc., and X-70-092 and X-70-093 from Shin-Etsu Chemical Co.,Ltd. Preferred surfactants are Florade FC-430 from Sumitomo 3M, Ltd.,KH-20 and KH-30 from Asahi Glass Co., Ltd., and X-70-093 from Shin-EtsuChemical Co., Ltd.

Pattern formation using the resist composition of the invention may becarried out by a known lithographic technique. For example, the resistcomposition is applied onto a substrate such as a silicon wafer by spincoating or the like to form a resist film having a thickness of 0.2 to2.0 μm, which is then pre-baked on a hot plate at 60 to 150° C. for 1 to10 minutes, and preferably at 80 to 130° C. for 1 to 5 minutes. Apatterning mask having the desired pattern is then placed over theresist film, and the film exposed through the mask to an electron beamor to high-energy radiation such as deep-UV rays, an excimer laser, orx-rays in a dose of about 1 to 200 mJ/cm², and preferably about 5 to 100mJ/cm², then post-exposure baked (PEB) on a hot plate at 60 to 150° C.for 1 to 5 minutes, and preferably at 80 to 130° C. for 1 to 3 minutes.Finally, development is carried out using as the developer an aqueousalkali solution, such as a 0.1 to 5% (preferably 2 to 3%) aqueoussolution of tetramethylammonium hydroxide (TMAH), this being done by aconventional method such as dipping, puddling, or spraying for a periodof 0.1 to 3 minutes, and preferably 0.5 to 2 minutes. These steps resultin the formation of the desired pattern on the substrate. Of the varioustypes of high-energy radiation that may be used, the resist compositionof the invention is best suited to fine pattern formation with, inparticular, deep-UV rays having a wavelength of 248 to 193 nm, anexcimer laser, x-rays, or an electron beam. The desired pattern may notbe obtainable outside the upper and lower limits of the above range.

The resist composition comprising the polymer as a base resin lendsitself to micropatterning with electron beams or deep-UV rays since itis sensitive to high-energy radiation and has excellent sensitivity,resolution, and etching resistance. Especially because of the minimizedabsorption at the exposure wavelength of an ArF or KrF excimer laser, afinely defined pattern having sidewalls perpendicular to the substratecan easily be formed.

EXAMPLE

Synthesis Examples and Examples are given below by way of illustrationand not by way of limitation. The abbreviation Mw is a weight averagemolecular weight, SEM is scanning electron microscope, and TMAH istetramethylammonium hydroxide.

Polymers within the scope of the invention were synthesized by thefollowing procedure.

Synthesis Example 1

Synthesis of Polymer 1

In 150 ml of tetrahydrofuran were dissolved 15.4 g of3,5,10-trioxatricyclo[5.2.1.0^(2,6)]-8-decen-4-one (synthesized byeffecting Diels-Alder reaction on furan and vinylene carbonate), 104.0 gof 2-ethyl-2-norbornyl 5-norbornene-2-carboxylate and 49.0 g of maleicanhydride. To the solution was added 1.8 g of2,2′-azobisisobutyronitrile. The solution was stirred for 15 hours at60° C. and then concentrated in vacuum. The residue was dissolved in 400ml of tetrahydrofuran, which was added dropwise to 10 liters ofn-hexane. The resulting solids were collected by filtration, washed with10 liters of n-hexane, and vacuum dried for 6 hours at 40° C. There wasobtained 72.9 g of a polymer designated Polymer 1 whose structure isshown below. The yield was 43.3%.

Synthesis Examples 2 to 12

Synthesis of Polymers 2 to 12

Polymers 2 to 12 were synthesized by the same procedure as above or awell-known procedure:

Example I

Resist compositions were formulated using inventive polymers as the baseresin and examined for substrate adhesion.

Examples I-1 to I-4 and Comparative Examples I-1, 2

Resist compositions were prepared by using inventive polymers (Polymers1 to 4) or comparative polymers (Polymers 13 and 14 identified below) asthe base resin, and dissolving the polymer, a photoacid generator(designated as PAG1), and a basic compound in a solvent in accordancewith the formulation shown in Table 1. These compositions were eachfiltered through a Teflon filter (pore diameter 0.2 μm), thereby givingresist solutions:

These resist solutions were spin coated onto hexamethyldisilazane-spraycoated silicon wafers at 90° C. for 40 seconds, then heat treated at110° C. for 90 seconds to give resist films having a thickness of 0.5μm. The resist films were exposed using an KrF excimer laser stepper(Nikon Corporation; NA 0.5), then heat treated at 110° C. for 90seconds, and puddle developed with a solution of 2.38% TMAH in water for60 seconds, thereby giving 1:1 line-and-space patterns. The wafers asdeveloped were observed under overhead SEM. The minimum width (μm) oflines left unstrapped is the limit of adhesion of the resist under test.

The composition and test results of the resist materials are shown inTable 1.

The solvent and basic compound used are propylene glycol methyl etheracetate (PGMEA) and tributyl amine (TBA), respectively. It is noted thatthe solvent contained 0.01% by weight of surfactant KH-20 (Asahi GlassCo., Ltd.).

TABLE 1 Photoacid Basic Limit of Resin generator compound Solventadhesion (pbw) (pbw) (pbw) (pbw) (μm) Example I-1 Polymer 1 PAG 1 TBAPGMEA 0.24 (80) (1) (0.078) (480) Example I-2 Polymer 2 PAG 1 TBA PGMEA0.26 (80) (1) (0.078) (480) Example I-3 Polymer 3 PAG 1 TBA PGMEA 0.26(80) (1) (0.078) (480) Example I-4 Polymer 4 PAG 1 TBA PGMEA 0.26 (80)(1) (0.078) (480) Comparative Polymer PAG 1 TBA PGMEA >0.50 Example I-113 (80) (1) (0.078) (480) Comparative Polymer PAG 1 TBA PGMEA >0.50Example I-2 14 (80) (1) (0.078) (480)

It is evident from Table 1 that the polymers within the scope of theinvention have good substrate adhesion.

Example II

Resist compositions were formulated using inventive polymers as the baseresin and examined for swell.

Examples II-1 to II-4 and Comparative Examples II-1, 2

Resist compositions were prepared as above in accordance with theformulation shown in Table 2. The resist solutions were spin coated ontohexamethyldisilazane-spray coated silicon wafers at 90° C. for 90seconds, then heat treated at 110° C. for 90 seconds to give resistfilms having a thickness of 0.5 μm. The resist films were exposed usingan KrF excimer laser stepper (Nikon Corporation; NA 0.5), then heattreated at 110° C. for 90 seconds, and dip developed with a solution of2.38% TMAH in water for 200 seconds. After the wafers were developed,the film thickness was measured at exposure spots. A maximum thicknessincrease (in Å) is reported as the swell.

The composition and test results of the resist materials are shown inTable 2.

The solvent and basic compound used are propylene glycol methyl etheracetate (PGMEA) and tributyl amine (TBA), respectively. It is noted thatthe solvent contained 0.01% by weight of surfactant KH-20 (Asahi GlassCo., Ltd.).

TABLE 2 Photoacid Basic Resin generator compound Solvent Swell (pbw)(pbw) (pbw) (pbw) (Å) Example II-1 Polymer 1 PAG 1 TBA PGMEA ≦0 (80) (1)(0.078) (480) Example II-2 Polymer 2 PAG 1 TBA PGMEA ≦0 (80) (1) (0.078)(480) Example II-3 Polymer 3 PAG 1 TBA PGMEA ≦0 (80) (1) (0.078) (480)Example II-4 Polymer 4 PAG 1 TBA PGMEA ≦0 (80) (1) (0.078) (480)Comparative Polymer 13 PAG 1 TBA PGMEA 181 Example II-1 (80) (1) (0.078)(480) Comparative Polymer 14 PAG 1 TBA PGMEA 89 Example II-2 (80) (1)(0.078) (480)

It is evident from Table 2 that the polymers within the scope of theinvention have good swell-suppressing effect.

Example III

Resist compositions were formulated using inventive polymers andexamined for resolution upon KrF excimer laser exposure.

Examples III-1 to III-21 Evaluation of Resist Resolution

Resist compositions were prepared by using Polymers 1 to 12 as the baseresin, and dissolving the polymer, a photoacid generator (designated asPAG1 and 2), a dissolution regulator (designated as DRR1 to 4), a basiccompound, and a compound having a ≡C—COOH group in the molecule (ACC1and 2) in a solvent in accordance with the formulation shown in Table 3.These compositions were each filtered through a Teflon filter (porediameter 0.2 μm), thereby giving resist solutions:

The solvent and basic compounds used are as follows. It is noted thatthe solvent contained 0.01% by weight of surfactant KH-20 (Asahi GlassCo., Ltd.).

PGMEA: propylene glycol methyl ether acetate

TEA: triethanolamine

TMMEA: trismethoxymethoxyethylamine

TMEMEA: trismethoxyethoxymethoxyethylamine

These resist solutions were spin coated onto hexamethyldisilazane-spraycoated silicon wafers at 90° C. for 90 seconds, then heat treated at110° C. for 90 seconds to give resist films having a thickness of 0.5μm. The resist films were exposed using an KrF excimer laser stepper(Nikon Corporation; NA 0.5), then heat treated at 110° C. for 90seconds, and puddle developed with a solution of 2.38% TMAH in water for60 seconds, thereby giving 1:1 line-and-space patterns.

The wafers as developed were sectioned and observed under sectional SEM.The optimal dose (Eop, mJ/cm²) was defined as the dose which provided a1:1 resolution at the top and bottom of a 0.30 μm line-and-spacepattern. The resolution of the resist under evaluation was defined asthe minimum line width (μm) of the lines and spaces that separated atthe optimal dose. The shape of the resolved resist pattern was examinedunder a SEM.

The composition and test results of the resist materials are shown inTable 3.

TABLE 3 Photoacid Dissolution Basic Resin generator regulator compoundSolvent Eop Resolution Example (pbw) (pbw) (pbw) (pbw) (pbw) (mJ/cm²)(μm) Shape III-1 Polymer 1 PAG 1 — TEA PGMEA 27.0 0.20 rectangular (80)(1) (0.063) (480) III-2 Polymer 2 PAG 1 — TEA PGMEA 26.0 0.22rectangular (80) (1) (0.063) (480) III-3 Polymer 3 PAG 1 — TEA PGMEA24.0 0.22 rectangular (80) (1) (0.063) (480) III-4 Polymer 4 PAG 1 — TEAPGMEA 25.0 0.22 rectangular (80) (1) (0.063) (480) III-5 Polymer 5 PAG 1— TEA PGMEA 25.0 0.20 rectangular (80) (1) (0.063) (480) III-6 Polymer 6PAG 1 — TEA PGMEA 23.0 0.22 rectangular (80) (1) (0.063) (480) III-7Polymer 7 PAG 1 — TEA PGMEA 24.0 0.20 rectangular (80) (1) (0.063) (480)III-8 Polymer 8 PAG 1 — TEA PGMEA 21.0 0.20 rectangular (80) (1) (0.063)(480) III-9 Polymer 9 PAG 1 — TEA PGMEA 20.0 0.22 rectangular (80) (1)(0.063) (560) III-10 Polymer 10 PAG 1 — TEA PGMEA 19.0 0.20 rectangular(80) (1) (0.063) (560) III-11 Polymer 11 PAG 1 — TEA PGMEA 29.0 0.20rectangular (80) (1) (0.063) (480) III-12 Polymer 12 PAG 1 — TEA PGMEA32.0 0.22 rectangular (80) (1) (0.063) (480) III-13 Polymer 5 PAG 2 —TEA PGMEA 27.0 0.20 rectangular (80) (1) (0.063) (480) III-14 Polymer 5PAG 2 — TMMEA PGMEA 28.0 0.20 rectangular (80) (1) (0.118) (480) III-15Polymer 5 PAG 2 — TMEMEA PGMEA 28.0 0.20 rectangular (80) (1) (0.173)(480) III-16 Polymer 1 PAG 2 DRR 1 TEA PGMEA 23.0 0.22 rectangular (70)(1) (10) (0.063) (480) III-17 Polymer 1 PAG 2 DRR 2 TEA PGMEA 25.0 0.22rectangular (70) (1) (10) (0.063) (480) III-18 Polymer 1 PAG 2 DRR 3 TEAPGMEA 30.0 0.22 rectangular (70) (1) (10) (0.063) (480) III-19 Polymer 1PAG 2 DRR 4 TEA PGMEA 24.0 0.20 rectangular (70) (1) (10) (0.063) (480)III-20 Polymer 1 PAG 2 ACC 1 TEA PGMEA 25.0 0.22 rectangular (80) (1)(4) (0.063) (480) III-21 Polymer 1 PAG 2 ACC 2 TEA PGMEA 29.0 0.22rectangular (80) (1) (4) (0.063) (480)

It is seen from Table 3 that the resist compositions within the scope ofthe invention have a high sensitivity and resolution upon KrF excimerlaser exposure.

Example IV

Resist compositions were formulated using inventive polymers andexamined for resolution upon ArF excimer laser exposure.

Examples IV-1 to IV-2 Evaluation of Resist Resolution

Resist compositions were prepared as in Example III in accordance withthe formulation shown in Table 4.

The resulting resist solutions were spin coated ontohexamethyldisilazane-spray coated silicon wafers at 90° C. for 90seconds, then heat treated at 110° C. for 90 seconds to give resistfilms having a thickness of 0.5 μm. The resist films were exposed usingan ArF excimer laser stepper (Nikon Corporation; NA 0.55), then heattreated at 110° C. for 90 seconds, and puddle developed with a solutionof 2.38% TMAH in water for 60 seconds, thereby giving 1:1 line-and-spacepatterns.

The wafers as developed were sectioned and observed under sectional SEM.The optimal dose (Eop, mJ/cm²) was defined as the dose which provided a1:1 resolution at the top and bottom of a 0.25 μm line-and-spacepattern. The resolution of the resist under evaluation was defined asthe minimum line width (μm) of the lines and spaces that separated atthe optimal dose. The shape of the resolved resist pattern was examinedunder a SEM.

The composition and test results of the resist materials are shown inTable 4. It is noted that the solvent and basic compounds in Table 4 areas follows. It is noted that the solvent contained 0.01% by weight ofsurfactant KH-20 (Asahi Glass Co., Ltd.).

PGMEA: propylene glycol methyl ether acetate

TEA: triethanolamine

TMMEA: trismethoxymethoxyethylamine

TABLE 4 Photo- acid Reso- Ex- gene- Basic Eop lu- am- Resin ratorcompound Solvent (mJ/ tion ple (pbw) (pbw) (pbw) (pbw) cm²) (μm) ShapeIV-1 Polymer PAG 1 TEA PGMEA 16.0 0.15 rectan- 5 (80) (1) (0.063) (480)gular IV-2 Polymer PAG 2 TMMEA PGMEA 17.0 0.15 rectan- 5 (80) (1)(0.118) (480) gular

It is seen from Table 4 that the resist compositions within the scope ofthe invention have a high sensitivity and resolution upon ArF excimerlaser exposure.

Japanese Patent Application No. 2000-372406 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

What is claimed is:
 1. A polymer comprising recurring units of thefollowing general formula (1) and/or (2) and having a weight averagemolecular weight of 1,000 to 500,000:

wherein R¹ and R² each are hydrogen, a straight, branched or cyclicalkyl, acyl or alkylsulfonyl group of 1 to 15 carbon atoms or astraight, branched or cyclic alkoxycarbonyl or alkoxyalkyl group of 2 to15 carbon atoms, in which some or all of the hydrogen atoms onconstituent carbon atoms may be substituted with halogen atoms, R³ andR⁴ each are hydrogen, a straight, branched or cyclic alkyl or alkoxygroup of 1 to 15 carbon atoms, or a straight, branched or cyclicalkoxyalkyl group of 2 to 15 carbon atoms, in which some or all of thehydrogen atoms on constituent carbon atoms may be substituted withhalogen atoms, and R³ and R⁴ may together bond with the carbon atom toform an aliphatic ring having 4 to 8 carbon atoms, or R³ and R⁴, takentogether, may be an oxygen atom, k is 0 or
 1. 2. The polymer of claim 1comprising, in addition to the recurring units of formula (1) and/or(2), recurring units of the following general formula (3):

wherein R⁵ is hydrogen, methyl or CH₂CO₂R⁷, R⁶ is hydrogen, methyl orCO₂R⁷, R⁷ is a straight, branched or cyclic alkyl group of 1 to 15carbon atoms, R⁸ is an acid labile group, R⁹ is selected from the classconsisting of a halogen atom, a hydroxyl group, a straight, branched orcyclic alkoxy, acyloxy or alkylsulfonyloxy group of 1 to 15 carbonatoms, and a straight, branched or cyclic alkoxycarbonyloxy oralkoxyalkoxy group of 2 to 15 carbon atoms, in which some or all of thehydrogen atoms on constituent carbon atoms may be substituted withhalogen atoms, Z is a single bond or a straight, branched or cyclic(p+2)-valent hydrocarbon group of 1 to 5 carbon atoms in which at leastone methylene may be substituted with oxygen to form a chain-like orcyclic ether or two hydrogen atoms on a common carbon may be substitutedwith oxygen to form a ketone, k is 0 or 1, and p is 0, 1 or
 2. 3. Thepolymer of claim 1 comprising, in addition to the recurring units offormula (1) and/or (2), recurring units of the following generalformulae (3) and (4):

wherein k, p and R⁵ to R⁹ are as defined above, Y is —O— or —(NR¹⁰)—,and R¹⁰ is hydrogen or a straight, branched or cyclic alkyl group of 1to 15 carbon atoms.
 4. The polymer of claim 1 comprising, in addition tothe recurring units of formula (1) and/or (2), recurring units of thefollowing general formula (5) alone or in combination with recurringunits of the following general formula (3), and recurring units of thefollowing general formula (4):

wherein k, p, R⁵ to R⁹ and Y are as defined above.
 5. A resistcomposition comprising the polymer of claim
 1. 6. A process for forminga resist pattern comprising the steps of: applying the resistcomposition of claim 5 onto a substrate to form a coating, heat treatingthe coating and then exposing it to high-energy radiation or electronbeams through a photo mask, and optionally heat treating the exposedcoating and developing it with a developer.